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%la fi /M2 ATTO R N EY United States Patent 3,519,246 HOISTING UNIT Hartley Belding, Rte. 1, Box 29B, Bartlett, Ill. 60103 Filed June 28, 1968, Ser. No. 741,134 Int. Cl. B66d 1/00 U.S. Cl. 254-135 6 Claims ABSTRACT OF THE DISCLOSURE A gantry jack or similar hoisting unit having hydraulic lift means and means to successively engage with a load carrying chain to incrementally elevate the chain and its load. The hydraulic lift means includes lock means to prevent inadvertent lowering of the load when hydraulic pressure is relieved.

This invention relates to improvements in gantry jacks and the like, and is more particularly concerned with the novel construction of such apparatus wherein the load is incrementally raised through the vertically reciprocable action of a pawl carrying headplate associated with a load carrying chain. During periodic retraction of the headplate, auxiliary pawls carried by the body of the appara tus function to support the load. At all times during operation of the jack, novel load lock devices function to prevent inadvertent retraction of the headplate.

It is, therefore, an object of the invention to provide a gantry jack of the character referred to.

Another object is to provide a gantry jack of the character referred to having a headplate assembly of novel construction.

Another and further object is to provide novel auxiliary means in a hydraulically actuated gantry jack to support the load.

Still another object is to provide a gantry jack of the character referred to which is ruggedly constructed, simple and inexpensive to manufacture and to operate, and very efiicient in use.

The structure by means of which the above noted and other objects and advantages of the invention are attained will be described in the following specification, taken in conjunction with the accompany drawings, showing a preterred illustrative embodiment of the invention, in which:

FIG. 1 is aside elevational view of a gantry jack embodying the invention;

FIG. 2 is an end elevational view thereof;

FIG. 3 is a side elevational view, with the wheel carriers removed and parts in section, showing the headplate in a lowered position;

FIG. 4 is a view similar to FIG. 3, showing the headplate in an elevated-position; and

FIG. 5 is a detail sectional view of one of the lock nuts.

Referring to the exemplary disclosure of the invention as shown in the accompanying drawings, the gantry jack, generally indicated at 11, is mounted to travel along horizontally arranged tracks 12 constituting part of an overhead structure. The gantry jack may be moved along said tracks by means of any suitable structure not forming a part of the invention and consequently not shown.

In general, the gantry jack 11 comprises a body 13 having laterally projecting axles 14 upon each of which is mounted a wheel carrier 15 with wheels 16 that rest upon and travel along the tracks 12. The body 13 includes a pair of vertically disposed cylinders 17, closed at their bottom ends and having communication with a source of hydraulic pressure through conduits 17a.

The body 13 has a central passageway 18 through which the hoist chain 19 extends. This chain is comprised of pairs of links 21 connected by single links 22 by means of pivotal pins 23. The chain is so disposed in the passageway 18 that its fiat sides face the lateral sides of the body. The body 13 carries on its top surface a pair of heavy duty pawls 24 journalled therein at 25 and extending in an upward direction generally, one on each side of the chain 19. The journal for each pawl carries on its outside an arm or lug 26. These lugs are connected to opposite ends of a piston-cylinder assembly 27 operable to rock the pawls from a substantially vertical position into inclined positions for engagement with the lower end of one of the single links 22.

The gantry jack also includes a headplate 28 carried on the upper ends of a pair of piston rods 29 that extend downwardly into the respective cylinders 17. These rods 29 function when hydraulic pressure is admitted into the lower ends of the cylinders, to raise the headplate 28 from a lowered position into an elevated position. The headplate 28 also carries a pair of heavy duty pawls 31, journalled therein by journals 32, one on each side of the chain 19 which extends upwardly through an opening 33 in the headplate. These pawls are interconnected by a piston-cylinder assembly 34 which operates to move the pawls from a substantially vertical position into inclined positions in engagement with the lower end of one of the single links 22.

Insofar as the structure has been described, the operation is substantially as follows:

With the headplate in its lowermost position as best shown in FIG. 3, and its pawls 31 out of engagement with the chain, the pawls 24 are engaged with the chain to support a load carried thereby. The pawls 31 are now moved into engagement with the chain and hydraulic pressure is admitted into the lower end of each cylinder 17. As the hydraulic pressure forces the piston rods 29 upwardly, the headplate is raised. Because of the engagement of pawls 31 with the chain, the chain is raised therewith while at the same time the load pawls 24 are moved into disengaged position. When the chain has been lifted the maximum distance of travel of the headplate (FIG. 4), pawls 31 are disengaged and hydraulic pressure in the cylinders is relieved. This allows the headplate to return to its lowermost position (FIG. 3) whereupon its pawls 31 again engage with the chain and the lifting cycle is repeated to elevate the chain another increment. Raising and lowering of the headplate is repeated as often as is necessary to elevate the load to its required elevation.

To lower the load, after it has been relocated by movement of the gantry jack along its tracks, the sequence of operation is reversed. That is, the headplate 28, if not already in its raised position, is carried into its elevated position and its pawls 31 are engaged with the chain. The pawls 24 are disengaged and the hydraulic pressure in cylinders 16 is gradually reduced to allow the headplate to move downwardly carrying the chain with it. When the headplate is in its lowermost position, the pawls 24 are engaged with the chain to support the load while the pawls 31 are released and the headplate is again elevated. This cycle is repeated until the load is returned to a support surface.

In order to assist the hydraulic pressure in supporting the load, each of the piston rods 29 has associated with it a lock nut structure. This structure involves the provision of external threads on each piston rod. Meshed therewith is a lock nut 35 which, as best shown in FIG. 5, comprises an internally threaded collar 36 having an external flange 37 on its lower end that is trapped in an annular recess 38 formed in the body 13. The upper or protruding end of the collar 36 carries a gear 39 with which a worm gear 41 (FIG. 2) is meshed at all times. The worm gears of each assembly are carried by a common shaft 42 connected to a motor 43. The motor 43 preferably is a hydraulic motor and it is operable in both directions. During raising or lowering of the headplate and its piston rods the lock nuts 35 are rotated in a direction to permit the rods to move in the intended direction. Should there be any failure of hydraulic pressure or a lessening thereof, the lock nuts 35 will carry the load. This is particularly useful in those situations where the load is suspended for a period of time While the gantry jack is being moved along the tracks, or should the load be required to be suspended for a period during which work is being performed thereon.

Conventional automatic or manual controls including limit switches and solenoid operated hydraulic valves may be provided to afford coordinated operation of the various components of the assembly.

Although I have described a preferred embodiment of my invention, in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as details of the structure may be modified or changed Without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact construction described.

I claim:

1. A gantry jack comprising, in combination, a body having an opening therein, hydraulic cylinders on said body, a load carrying chain extending upwardly through said opening, two pawls pivotally mounted on said body selectively engagea-ble with said chain, a hydraulic piston-cylinder assembly common to said pawls for moving them in unison into and out of engagement with the chain, a headplate, said headplate having an opening therethrough through which the chain extends, pistons carried by the headplate and operable in said cylinders, two pawls pivotally mounted on said headplate selectively engageable with said chain, and a hydraulic piston-cylinder assembly common to said pawls for moving them in unison into and out of engagement with the chain.

2. The gantry jack recited in claim 1, in which the gantry jack is mounted on wheels.

3. The gantry jack recited in claim 1, in which means is provided to lock the pistons in an elevated position.

4. The gantry jack recited in claim 1, in which each piston has lock nuts associated with it.

5. The gantry jack recited in claim 4, in which the pistons and their related lock nuts are threadingly engaged.

6. The gantry jack recited in claim 4, in which common screw means is operable to rotate the lock nuts in unison.

References Cited UNITED STATES PATENTS 1,117,516 11/1914 Petrie 254-135 1,168,935 1/1916 Davidson 187-8.47 1,740,692 12/1929 Hall 92-17 2,669,013 2/1954 Wilson 212-138 3,095,181 6/1963 Dromboski 254- 3,273,859 9/1966 Walli 254-109 3,309,062 3/1967 Jansz 92-17 FOREIGN PATENTS 221,439 5/ 1962 Austria.

HARVEY C. HORNSBY, Primary Examiner US. Cl. X.R. 

